Virax Mini VISIOVAL Manuel D'utilisation page 23

Surface Material
Brick, red rough
Brick, fireclay
Cast Iron, newly turned
Cast Iron, turned and heated
Chromium polished
Concrete
Concrete, rough
Concrete tiles
Cotton Cloth
Copper electroplated
Copper heated and covered with thick oxide layer
Copper Polished
Copper Nickel Alloy, polished
Glass smooth
Glass, Pyrex
Granite
Gypsum
Ice smooth
Ice rough
Caution: Values in emissivity tables are only ever guideline values.
Understanding the basic concept of Thermal Imaging:
It is important to understand that a thermal image represents the temperature distribution on
the surface of an object. This is important to understand when looking for concealed objects,
such as pipes embedded within floors or walls. You cannot look through objects with a
thermal camera, but rather you can detect a transfer of hot or cold from behind or within a
surface material. As this temperature differentiation is absorbed within the surface material the
ability to detect a thermal image of a concealed temperature variation will diminish. It may be
necessary to (for instance) start with a very cold floor, before turning on the heating element
embedded within the floor, in order to detech a temperature gradiant of the heating coils
within. Once the floor tile absorbs the heat with even distribution, it will no longer possible to
detect the temperature variations with your thermal camera. This would also apply to hot/cold
pipes concealed within walls.
NOTE: Actual temperature accuracy will vary, as the heat / cold is absorbed within the surface
material, as you are actually measuring the temperature on the surface material (not the pipe
concealed within).
Emissivity (ε) is a coefficient to measure the ability of a material to emit infrared radiation. This
is a critical setting within any thermal camera, in order to provide an accurate calculation of
vastly different materials (see attached table above). There are numerous factors taken into
account when selecting the proper Emissivity, which include color, finish and texture.
Generally speaking, polished surfaces reflect more strongly than rough or matt surfaces made
of the same material. It is important to select the proper Emissivity in order to obtain the
greatest thermal accuracy.
Emissivity
Surface Material
Coefficient
0.93 Rubber, hard glossy plate
0.75 Rubber Nat Hard
0.44 Rubber Nat Soft
0.60 - 0.70 Sand
0.058 Sawdust
0.85 Steel Oxidized
0.94 Steel Polished
0.63 Stainless Steel, weathered
0.77 Stainless Steel, polished
0.03 Stainless Steel, type 301
0.78 Steel Galvanized Old
0.023 - 0.052 Steel Galvanized New
0.059 Tile
0.92 - 0.94 Water
0.85 - 0.95 Wood Beech, planned
0.45 Wood Oak, planned
0.85 Wood, Pine
0.966 Wrought Iron
0.985
EN
Emissivity
Coefficient
0.94
0.91
0.86
0.76
0.75
0.79
0.07
0.85
0.075
0.54 - 0.63
0.88
0.23
0.97
0.95 - 0.963
0.935
0.885
0.95
0.94
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